In recent years the concern over energy consumption and the cost of fuel has resulted in a tremendous increase in the use of wood stoves, fireplace inserts, and the like as a means for providing auxiliary domestic heating. As a result, the increased need for firewood, and the proximity of firewood to the consumer has resulted in the evolvement of commerical firewood businesses. The commerical processing of firewood naturally dictates that improved high speed processing equipment for sawing firewood pieces from logs must be made available in order to make the business commercially feasible. There have been several attempts in the past to design and develop firewood cutting or sawing systems. A representative sample of patents illustrating such attempts at commerical firewood cutting machines includes U.S. Pat. Nos. 3,550,653, issued Dec. 29, 1970; 4,269,242, issued May 26, 1981; and 4,173,237, issued Nov. 6, 1979.
In each of the above patents, as well as in all of the other known attempts at developing improved firewood cutting operations, a log is placed on some type of longitudinal conveyance apparatus, progressed to a stop, and presented to a circular blade or chain saw spaced from the stop to cut off a prescribed length of wood from the initial end of the log being cut. Upon completion of the cut, the saw is removed from the path of the log, the log indexed forwardly to the stop, and then the cutting operation repeated to provide a second firewood piece. The above operation is repeated until the log is cut into several pieces. As is evident, while this speeds up the cutting operation substantially, it is still relatively slow in that only one firewood piece is cut with each sawing step. Therefore, recognizing this problem, the present invention adopts a cutting system in which the log is presented to a plurality of spaced saws by moving the log in a direction transverse to its longitudinal axis, whereupon the log is simultaneously cut into a plurality of shorter firewood pieces.
While this may seem to be a simple procedure, it is not. Such a technique presents subtle problems which must be solved in order to make such a procedure operate successfully. For example, the log must be continuously urged through the saw blades during the sawing operation, or else it will be kicked rearwardly. A complication in this step resides in the fact that logs are by nature not necessarily straight. In addition, downward pressure must be exerted on the log during the entire cutting operation, or else the log may be kicked upwardly. Therefore, as can be easily seen and appreciated, it is necessary to have complete control over the log once it is engaged by the teeth of the saw blade, or else extremely hazardous consequences may result. Toward this end, in accordance with the present invention, cleats or lugs on the feed conveyor exert a continuous forward pressure on the logs and follow it into and through the path of the saw blades. Also, and simultaneously, downward pressure is exerted on the log as the cutting operation begins. This downward pressure is exerted in either or both of two ways. First, a spring means in the path of the log engages the log and biases the log downwardly during the cutting operation. Secondly, downward pressure is exerted as a result of the relative position of the saw blade with respect to the log. In this regard the saw blade is positioned so that the center of the cutting blade is above the level of the log. Therefore, the saw blade is moving downwardly and forwardly as it engages the wood of the log.
Another problem exists in the support of the saws themselves along a common axis. The most straightforward way to accomplish this would be, of course, to mount the saws along a common shaft which extends through the center of all saws and drive the shaft at one end by a pulley from the output shaft of a motor. However, while possible, in reality this presents at least two major problems. First to generate enough torque at one end to drive all saws evenly is difficult. Secondly, the blades and/or pulley belts are relatively quick to wear out. If the blades are mounted on a common shaft, access to the interior blades for removal is difficult. Therefore, in the present invention each saw in the array is independently mounted from a support structure and each saw is driven by its own pulley attached by a belt or chain to a corresponding pulley on a common drive shaft. There are a plurality of pulleys secured to the common drive shaft in accordance with a uniquie spacing pattern, so that the lengths of firewood into which the logs are sawed may be easily changed without moving pulleys.
It is also preferable that all logs be presented to the array of cutting blades with the initial end of each log spaced from the first saw blade a constant prescribed distance, so that the firewood piece which is formed between the initial end and the first saw blade is of a known and consistent length. The opposite end of the logs will of course vary depending upon the length of the logs; however, only one scrap piece will result from each log. Toward this end, before the logs are fed to the sawing mechanism they are all moved longitudinally to a bumper and therefore the initial end of each log proceeds into the sawing mechanism in a common plane.
In accordance, then, with the broadest aspect of the present invention, there is provided an apparatus for sawing firewood pieces which includes a feed conveyor means for advancing logs in serially spaced arrangement in a direction transverse to the longitudinal axis of the logs to a discharge end. A sawing means is positioned adjacent the discharge end of the feed conveyor for receiving logs discharged therefrom. The sawing means preferably includes an array of longitudinally spaced, circular saws mounted along a common axis which axis, in turn, extends parallel to the longitudinal axis of the incoming logs.
In a preferred embodiment, the saws are individually mounted and include a biasing device between each adjacent pair of saws for maintaining a constant forward and downward pressure on the logs as they pass through the sawing mechanism to prevent inadvertent discharge of one or more firewood pieces upwardly or rearwardly out of the sawing mechanism. In this preferred embodiment the biasing means first includes upstanding lugs or cleats on the feed conveyor for providing the necessary forward pressure on the logs during the sawing operation. Secondly, the downward pressure on the logs during the sawing operation is accomplished either by mounting the longitudinal axis to the saw at a horizontal level above the logs themselves or by providing a spring device between each pair of saw blades which engages the logs and provides a constant downward bias thereto during the sawing operations, or by utilizing both techniques.
Further, in the preferred embodiment, there is provided an aligning means in the form of a V-shaped trough extending across and immediately downstream of the discharge end of the loading deck into which the logs are initially delivered. A longitudinal conveyor or urging means moves the logs longitudinally down to a bumper at one end of the trough, whereupon they are tilted, dumped, or otherwise delivered onto a feed conveyor and presented to the sawing mechanism with the initial end of each log passing in a common plane and equally spaced from the first cutting blade.
While the above discussion, and the discussion in the remainder of the specification is primarily directed to a log cutting operation, it is apparent that the same concepts would be equally applicable to an apparatus which cuts boards into shorter lengths. Also, while it may be implied from the discussion hereinabove that the saws are equally spaced along the common axis, this is not necessary if it is not desired that all firewood pieces be of equal length. It can be easily seen that the distances between blades might be changed to provide some logs of one length, some of another, and some of even a third or fourth length. It is pointed out, however, that the basic concept of the present invention is the idea of presenting logs to a cutting apparatus in a direction transverse to the longitudinal axis of the log, so that a plurality of logs are simultaneously cut and to provide means for maintaining proper control over those logs during such cutting operation.
It is therefore an object to provide an improved commercial firewood cutting apparatus.
It is another object of the present invention to provide a firewood cutting apparatus of the type described in which logs are presented to a plurality of circular saws in such a manner that a plurality of firewood pieces are cut simultaneously as the log passes the saws.
A further object of the present invention is to provide a firewood cutting apparatus of the type described in which control is maintained over the logs as they pass the sawing mechanism to prevent inadvertent discharge of the one or more firewood pieces upwardly or rearwardly from the mechanism during the cutting operation.